[Brad]

Hooks are used to execute raw php code in the files.

Basicly that bit of code does this:

Checks if hooks are on in vboptions, checks if any hooks exist for that hook location.
If any hooks are found and enabled your custom php code is set to the $hook var
If there is php code set to $hook it is sent to eval for the php code to be executed, if not nothing is done and php moves on to the rest of the code in the file.